1. Field of the Invention
Exemplary embodiments of the present invention relate to a system and method of controlling a low-voltage DC/DC converter for an electric vehicle; and, particularly, to a system and method of controlling a low-voltage DC/DC converter for an electric vehicle, which control a low-voltage DC/DC converter to efficiently charge a low-voltage battery.
2. Description of Related Art
In general, a hybrid electric vehicle includes a power source and a drive motor powered by a battery, and may improve fuel efficiency with the aid of the motor driven by the voltage of the battery during a start or acceleration of the vehicle by applying the power source to a front wheel.
A superior control unit which collectively operates the electric vehicle is an HCU (Hybrid Control Unit) or a VCU (Vehicle Control Unit). The HCU or the VCU communicates with an MCU (Motor Control Unit), which is a subordinate control unit, to maintain torque and speed of the motor as a drive source and a torque generation amount, and communicates with an ECU (Engine Control Unit), which operates the engine to generate power for voltage generation as an auxiliary power source, to perform relay control related to engine start and fault diagnosis.
In addition, the HCU detects temperature, voltage, current, SOC (State Of Charge), etc. of the battery as a main power source and communicates with a BMS (Battery Management System) which manages all conditions of the battery, to maintain the torque and speed of the motor based on the SOC. Furthermore, the HCU communicates with a TCU (Transmission Control Unit), which determines and maintains a shift ratio based on vehicle speed and a driving intention, to cause a desired speed to be maintained. The communication between the HCU as a superior control unit and the subordinate control units is performed via CAN communication to exchange information and transmit and receive control signals with respect to each other.
Meanwhile, the electric vehicle includes a low-voltage DC/DC (direct current) converter, (e.g., a DC/DC converter) which generates a direct current by rectifying power of a high-voltage battery. Such a low-voltage DC/DC converter switches a high-voltage DC to generate an AC (alternating current), transforms the AC using a coil, a transformer, or a capacitance, and then rectifies the AC again to generate a DC, thereby serving to supply each electric device of the electric vehicle with the generated DC.
In general, a low-voltage DC/DC converter control system for an electric vehicle operates the low-voltage DC/DC converter without utilization of information regarding a low-voltage battery. For example, the low-voltage DC/DC converter may output a fixed voltage of about 14.3V by operating the low-voltage DC/DC converter control system. Therefore, since unnecessary power is consumed due to the continuous high-voltage output (that is, about 14.3V) of the low-voltage DC/DC converter, a mileage of the electric vehicle by one charge may be reduced.
In addition, the low-voltage DC/DC converter control system for an electric vehicle supplies charge power to the low-voltage battery, regardless of the state of the low-voltage battery. Thus, it may be difficult to efficiently manage discharge of the low-voltage battery caused by a dark current generating unit such as a black box mounted within the vehicle when the vehicle remains idle for a predetermined period of time. Furthermore, a battery life may be reduced due to overcharge and gassing phenomena by continuous charge of the low-voltage battery when the electric vehicle is charged.